Adjusted Earned Run Average (ERA+): This stat adjusts a pitcher's ERA for league and ballpark factors and puts it on a scale where 100 is average. The further over 100 a pitcher goes, the better.

On-Base Plus Slugging Plus (OPS+): This does the same thing for OPS allowed that ERA+ does for ERA. In the case of pitchers, it shows how well they suppressed hitting relative to their peers. The further below 100 their number is, the better.

Plate Discipline:Things like Zone% (percentage of pitches in the strike zone), Contact% (percentage of swings that made contact) and assorted swing rates allow for a snapshot of how pitchers attacked hitters and bent them to their will. These figures are available at FanGraphs.

Contact Quality: FanGraphs also breaks the quality of contact off pitchers into three categories: Soft%, Medium% and Hard%. High Soft% and low Hard% rates are best.

Exit Velocity (EV): A Statcast specialty that measures the speed of the ball off hitters' bats. It's another way to gauge how well pitchers suppress loud contact. The MLB average in 2017 was 86.6 miles per hour.

30. Aroldis Chapman, New York Yankees

As recently as 2014, hitters were whiffing on 41.9 percent of the swings they took at Aroldis Chapman's fastball. That number has since been declining and fell all the way to 27.2 percent in 2017.

At an MLB-best 100.1 mph, Chapman's velocity was just fine. But the gap between him and everyone else shrunk in 2017. What also didn't help is that he spent a good chunk of the year without his fastball's normal "rise."

However, that problem was corrected amid a torrid September. And even throughout the year, making contact against him remained relatively difficult and was often for naught anyway. He limited batted balls to 84.4 mph exit velocity and cut off easy power routes by making it impossible to pull the ball.

29. Dellin Betances, New York Yankees

Never mind a mere elephant. The raging Lovecraftian monster in the room is Dellin Betances' walk rate.

Simply by virtue of how difficult it is to coordinate a massive 6'8" frame, walks are always an eventuality when he's on the mound. And this year he just couldn't maintain consistent mechanics. His release points varied widely from game to game, and he was often missing the zone by a lot.

28. Steve Cishek, Tampa Bay Rays

Beyond his relatively small sample size, another caveat with Steve Cishek's 2017 is that he was a specialist. He threw 69 percent of his pitches against righty batters, one of the highest marks among righty pitchers.

All the same, he continued to reap benefits from a repertoire that's about sliders first and sinkers second. His ground-ball rate spiked to its highest level in years at 56.1 percent. He also enjoyed 83.3 mph exit velocity and an elite 23.3 hard-hit percentage.

Cishek also ran into more whiffs after jumping ship from the Seattle Mariners to the Tampa Bay Rays, as his K/9 jumped from 6.8 to 9.5. He had a newfound willingness to venture up in the zone, helping to induce more swings outside the zone.

27. Brandon Morrow, Los Angeles Dodgers

Similar to Steve Cishek, Brandon Morrow only worked so many innings and benefited from a frequent platoon advantage against right-handed hitters.

Said advantage wasn't nearly as frequent, however, as Morrow only threw about 60 percent of his pitches against righty batters. Another difference is in Morrow's dominance, which was more...well, more dominant.

He aired out his fastball to the tune of a 97.7 mph average and attacked hitters with both sliders and cutters. He forced hitters into a guessing game by keeping his heat high and his secondaries low, resulting in a 40.2 out-of-zone chase rate that only two relievers topped.

Contact against the former starter plummeted to an all-time low. And while he was lucky to escape with a goose egg in the home runs column, there were only a couple close calls.

26. Blake Parker, Los Angeles Angels

Blake Parker wasn't on many radars going into 2017. Now here he is coming of a season that deserves to be on everyone's radar.

Albeit in limited exposure, he'd flashed swing-and-miss stuff in the majors in years past. He took that act to a whole 'nother level in 2017, bumping his contact rate down to just 70.9 percent. That was aided by extra fastball velocity and more liberal use of a splitter that disappeared in the hitting zone.

Hitters who got a bat on Parker's offerings did run into a solid share of hard contact. But by mixing his pitches and working down in the zone, he saved face with above-average ground ball and pop-up rates.

A breakout at the age of 32 is a little late. But you know what they say about the relationship between late and never.

25. Yusmeiro Petit, Los Angeles Angels

After working as a reliable swingman between 2014 and 2016, Yusmeiro Petit was a reliable swingman with a dash of dominant reliever in 2017.

It helps that he's added velocity to his fastball over the years, but it's more so his deception that makes him a tough matchup. Hitters are just as likely to get a cutter, curveball or changeup as they are to get a fastball, and he makes his pitches tough to tell apart, to boot.

He was only average at avoiding contact, and any hitter who guessed right could hit him hard. But he caught a lot of guys looking at strike three and collected pop-ups at an elite rate.

There's no shaking the sense that Petit enjoyed a little too much success in 2017. But so much quality and so much quantity can't be dismissed out of hand.

24. Anthony Swarzak, Milwaukee Brewers

When he was younger, Anthony Swarzak was warned by veterans not to push his arm too hard. As he became a veteran himself, he started to question that.

"... I think these last few years I'm getting to that age where nothing is guaranteed for me, so I'm kind of letting it all out there, and I think I found another gear somewhere," he told Scott Merkin of MLB.com in March.

Hence, Swarzak's fastball going from 92-ish mph to an average of 94.7 mph. That gave him the ability to overpower hitters in the strike zone. Throw in liberal use of his slider, and his contact rate as a whole drifted further south than ever before.

One gripe is that Swarzak only managed contact to the tune of 87.2 mph exit velocity. He did, however, survive on an above-average pop-up rate.

23. Alex Claudio, Texas Rangers

Alex Claudio isn't your typical high-octane reliever. He averaged just 86.7 mph on his fastball and ranked 10th from the bottom among qualified relievers in K/9.

But you can get away with being hit when you're hard to hit well. That was Claudio's trick for survival in 2017. He induced an elite 66.7 GB%, and his 84.9 mph exit velocity encapsulates how much of the contact off him was soft, to boot.

His primary weapon was a sinker with elite arm-side run. He also mixed in healthy doses of changeups and sliders. That's three different speeds and movements that hitters had to contend with, and Claudio upped the ante by making them reach with his low-and-lower location pattern.

While Claudio wasn't used like a LOOGY—short for "Lefty One Out Guy"—one catch is that he did perform much better against lefties (.368 OPS) than against righties (.694 OPS).

22. Chris Rusin, Colorado Rockies

As a left-hander with a bit of a quirk in his delivery and a low-90s fastball, Chris Rusin has the profile of a LOOGY.

But a LOOGY he certainly was not. He earned all his innings. Hitters just couldn't make good contact against him, as he finished the year with a 58.5 GB% and the same hard contact rate as Dellin Betances.

These were the fruits of a different sort of attack than hitters typically see from relievers. Rusin was aggressive in the strike zone, but typically only at the knees with a three-pitch array that offered three different speeds and movements: sinker, cutter and changeup.

The fact that it worked is proof that one need not be an overpowering pitcher to be an overpowering reliever.

21. Tommy Kahnle, New York Yankees

Tommy Kahnle just keeps throwing harder as the years go by. This year, his 97.9 mph fastball was one of the hardest featured by any reliever.

Dealing with that was enough of a challenge for hitters. Kahnle only made things more difficult by keeping the count in his favor. He assaulted the strike zone and spent more time ahead in the count than usual. That helped put hitters on the defensive and allowed his chase rate to skyrocket.

His 93.3 mph fastball wasn't great by modern reliever standards. That made it relatively easy for hitters to make contact against him, which means he put a lot of trust in a Washington Nationals defense that wasn't always up to the task of fielding the ball.

But Albers wouldn't be here if he didn't deserve his share of the credit.

He went right at hitters with a repertoire that was heavy on sinkers and sliders. How good this approach worked is apparent in his contact management. He worked a 51.0 GB% and limited hitters to elite marks in exit velocity (82.6 mph), soft contact (30.9%) and hard contact (22.2%).

The walks are the big sore spot on his record. A good chunk of those came in the latter half of the year when his mechanics started to get a little wobbly. Given his track record, these issues probably aren't going away.

But, no matter. The best relievers are the ones who overwhelm batters. Edwards showed in 2017 that he can handle that.

18. Wade Davis, Chicago Cubs

It's no accident that walks became a problem for Wade Davis in 2017. His rate of in-zone pitches plummeted well below the MLB average to a place where few other relievers dwelled.

This could hint at diminished confidence in stuff that doesn't quite have the same snap that it did during his glory days with the Kansas City Royals. Regardless, it spelled the end of what had been one of his key skills.

On the bright side, avoiding the strike zone had a hand in him avoiding contact like never before. And while hard contact wasn't impossible to come by, he remained proficient at jamming hitters. He had an elite soft-hit rate and limited all contact to an average of 84.8 mph.

The Davis of 2014-2015 is likely gone for good. The Davis of 2017, however, was still something special.

However, 2017 was another case of nobody being able to hit the guy when he's healthy. He worked a below-average contact rate and survived a barrage of balls in the air largely because said balls tended to leave bats with a whimper. His 82.1 mph exit velocity was third among relievers.

Thing is, that's no ordinary fastball. Beyond having mid-90s velocity, it also has elite rising action that plays well up in the zone. Hitters can't lay off it and can't hit it.

16. Ken Giles, Houston Astros

Ken Giles had a rough introduction with the Houston Astros in 2016, putting up a 4.11 ERA and allowing eight home runs. Suffice it to say, his second season in Houston went a lot better.

He gained velocity on his already blistering fastball, bringing it to an elite average of 98.1 mph. But the real change was in how he attacked hitters. By throwing more sliders for strikes, he threw more strikes, period.

This cost him some strikeouts, but he managed an excellent 67.8 Contact% anyway and reaped the benefits of a consistent flow of quiet contact. His exit velocity was a good-not-great 86.5 mph, but both his soft and hard contact rates were never better.

15. Raisel Iglesias, Cincinnati Reds

Raisel Iglesias showed a talent for missing bats when the Cincinnati Reds introduced him as a starter in 2015, so there always was the possibility of him being a menace in a relief role.

That notion came true in 2017 largely thanks to Iglesias' fastball. Its velocity jumped to an average of 96.4 mph, and he was more aggressive with his use of it. That helped him pound thestrike zone more frequently.

Iglesias mostly kept his slider and changeup on the same low trajectory as his fastball, so hitters at least had a good idea of where to look for something to hit. However, they were liable to be ambushed by high heat. And even if they guessed slider or changeup, hitting either was no easy task.

Ultimately, he largely avoided contact in general and hard contact when the ball was put in play.

14. Archie Bradley, Arizona Diamondbacks

To some extent, it's fair to raise a suspicious eyebrow over Archie Bradley's dominant results.

With a 78.8 Contact%, he didn't elude bats better than the average pitcher. While his 87.5 mph exit velocity wasn't terrible, that was also worse than average.

One thing he did very well, however, was not beat himself. Few relievers were more aggressive in the strike zone, helping him to his low walk rate. And he could get away with that act because, with a 96.4 mph fastball and hard curveball, his stuff was simply overpowering.

Evidence of this is found in where batters hit Bradley's pitches. He had one of the lowest pull rates of any reliever, resulting in both lefties and righties having to take the long ways to damage against him.

13. Chad Green, New York Yankees

One catch to Chad Green's dominance is that he faced only 31 hitters in high-leverage situations, 161 fewer than MLB leader Corey Knebel.

Another is that he was actually hit pretty hard. Batters averaged 89.3 mph exit velocity against him, helping to keep his hard contact rate way above average. On balance, he may have been fortunate to finish with such good results.

Of course, Green's elite 67.2 Contact% highlights how making contact against him was the hard part. Even when he was throwing strikes, as only Craig Kimbrel had a lower in-zone contact rate.

Pitching above the belt allowed Green's fastball to play even faster than its 95.8 mph velocity, resulting in an elite whiff-per-swing rate. If you're only going to have one dominant pitch, that's a good way to go.

12. Mike Minor, Kansas City Royals

Mike Minor had a rough season as a starter for the Atlanta Braves in 2014, underwent shoulder surgery in 2015 and then disappeared for a while.

This year, he was reborn as a completely different pitcher.

Switching to a relief role equipped his fastball with more velocity at an average of 94.4 mph. Just as important is how his slider gained both velocity and glove-side run, turning it into a nasty pitch that limited hitters to a .146 average. The lefty also featured a curveball and changeup.

While the catch is that he was better against lefties (.423 OPS) than righties (.664 OPS), Minor still finished with a below-average contact rate and 84.7 mph exit velocity. He was tough against all comers.

11. Pat Neshek, Colorado Rockies

Simply based on his funky delivery, a fastball that plays above its low-90s velocity and a slider that moves like a frisbee, Pat Neshek would be a tough at-bat under any circumstance.

What makes him tougher is that he doesn't give batters an inch. No reliever pounded the strike zone more often than he did this year, and he lived on the outer half against both lefties and righties. He thus rendered them always on guard and always having to reach for contact.

Making contact wasn't easy, but even harder was making good contact. Hitters struggled to pull his pitches and managed just 84.2 mph exit velocity to boot.

Righties especially felt Neshek's wrath, managing just a .486 OPS. But with a .614 OPS against lefties, he was no platoon specialist.

It looks the part of a nasty pitch to the naked eye, and nothing on paper disagrees. It has the kind of glove-side run that few other sliders have and produced some nifty results. Namely: a 45.4 whiff/swing rate and a .104 average against.

Between having to contend with both that and Hand's 93.5 mph fastball, it's no wonder hitters had a hard time with both contact and good contact against him. He had a below-average 70.6 Contact% and limited hitters to 85.7 mph exit velocity.

Hand also didn't have a platoon split. He held lefties to a .590 OPS, and righties to a .577 OPS.

9. Chris Devenski, Houston Astros

Chris Devenski is a big dude with a funky delivery and a mid-90s fastball. Sounds like your typical shutdown reliever, but he's different.

His ability to eat innings was one thing that separated him in 2017. Another was the degree to which he didn't rely on his fastball. Sliders and changeups accounted for the bulk of his offerings. The latter was downright obscene, disappearing on hitters and missing bats like few other relief changeups.

Devenski finished with the fifth-lowest contact rate among qualified relievers. He also mostly avoided hard contact, limiting hitters to 85.1 mph exit velocity and with good soft and hard contact rates.

One catch is that Devenski did tail off in the second half, when strikeouts and walks started coming in almost equal measures. However, he fought through that to post a 2.57 ERA anyway.

8. Ryan Madson, Washington Nationals

Ryan Madson was a good reliever in his long-awaited return from Tommy John surgery in 2015 and 2016. This year, he was back to being a truly great reliever for the first time since 2011.

It helped to have his best fastball velocity ever at 95.2 mph, but his excellence didn't stop there. He was a legit four-pitch pitcher with a four-seamer, sinker, changeup and curveball. That alone made him a rarity among relievers. To boot, all four pitches were good pitches.

Despite what his 1.4 BB/9 would suggest, Madson didn't actually throw more pitches in the strike zone. The real difference was a higher chase rate that also fed into his below-average contact rate.

And in limiting hitters to 84.9 mph exit velocity and elite soft and hard contact rates, hitting him well wasn't easy.

7. Roberto Osuna, Toronto Blue Jays

You might notice that Roberto Osuna's ERA+ isn't as good as the rest of his numbers. The Toronto Blue Jays defense is complicit in that. It was woefully inefficient and thus not very helpful to Osuna's BABIP.

The man himself was actually pretty good at suppressing loud contact, holding hitters to 85.9 mph exit velocity. He was also quite good at suppressing contact in general, posting a career-low 68.4 Contact%.

In past years, Osuna had gone right at hitters with a fastball that boasted mid-90s velocity and pretty good rise, effectively daring them to hit an unhittable pitch. His new trick this year was throwing his biting cutter about as often. The fastball set up the cutter and vice versa. One of the benefits was a huge chase rate.

6. David Robertson, New York Yankees

Only two relievers have accumulated more WAR since 2011 than David Robertson, and 2017 might have been his finest year yet.

He's always had an explosive cutter and a knee-buckling curveball. The difference this year was that he used them in more equal tandem, decreasing his use of the former and increasing his use of the latter.

His habit of burying curveballs in the dirt would, in theory, make this easier for hitters to work counts and draw walks. In reality, their inability to lay off helped drive his chase rate to an all-time high. That, in turn, drove his contact rate all the way down to 63.6 percent. Only two relievers were better at evading bats.

His contact management wasn't as impressive, but not quite a flaw either. He got by with perfectly average 86.6 mph exit velocity and a below-average hard contact rate.

4. Felipe Rivero, Pittsburgh Pirates

Felipe Rivero could sit in the mid-90s with his fastball in 2015 and 2016. In 2017, he kicked things up to an elite average of 98.5 mph and topped 100 more often than all but two pitchers.

But for as nasty as Rivero's fastball was, it wasn't actually his best pitch. He also featured a filthy changeup that drew whiffs on 53.6 percent of the swings taken at it, the highest rate of any relief changeup.

Rivero went right at hitters, throwing 50.6 percent of his pitches in the strike zone. His contact rate remained excellent, and the quality of contact off him decreased dramatically. He enjoyed a 52.9 GB% and exit velocity that dropped to 84.4 mph.

Nobody felt his wrath like left-handed batters. They managed just a .255 OPS against him, the lowest of any pitcher in MLB.

3. Andrew Miller, Cleveland Indians

It wasn't all good for Andrew Miller in 2017. He did miss some time with a knee injury, after all.

Otherwise, it was a typical Andrew Miller sort of year.

Already the stuff of legend, his slider got even better in 2017. It picked up more spin, pushing it even further up the ranks of high-spin sliders. This didn't make it harder to hit, but the extra spin had a hand in making it nigh impossible to hit well. Hitters averaged just 77.7 mph when they could put the lefty's slider in play.

That helped Miller lead all pitchers in overall exit velocity at 81.2 mph. And between his slider and his mid-90s fastball, he had all he needed to also boast an elite contact rate.

2. Kenley Jansen, Los Angeles Dodgers

With few exceptions, Kenley Jansen only throws cutters. And that's OK.

It's a filthy pitch with 93.3 mph velocity and movement that occurs precisely when it's entering the hitting zone. Batters thus have little time to react to a ball that's moved on by the time they actually react.

That affords Jansen the luxury of not having to mess around with hitters. He went at them with an elite strike zone percentage. He still managed an elite in-zone contact rate despite that, which fueled an elite overall contact rate.

Hard contact? Hardly. Balls off him averaged 83.8 mph, helping him to a soft contact rate that only Dellin Betances bested.

1. Craig Kimbrel, Boston Red Sox

Craig Kimbrel had a rough 2016 in part because his body betrayed him. A knee injury sidelined him for a good chunk of the summer and he dealt with a secret finger injury throughout.

He was back to good health in 2017. And also, back to business.

He maintained better mechanical consistency that allowed him to throw a lot more pitches in the strike zone. And since said pitches were an explosive 98.3 mph fastball and a filthy breaking ball, he enjoyed both a much-improved walk rate and the lowest in-zone contact rate of any reliever.

Since contact outside the zone was even harder to come by, hitters ultimately made contact on just 59.4 percent of their swings against him. That was easily the best of any reliever.

On the downside, hitters averaged a whopping 91.4 mph when they did put the ball in play off Kimbrel. But thanks to a low pull rate, lefties and righties wasted a lot of that to lesser power avenues.

All in all, there are good reasons Kimbrel was 2017's most dominant reliever.